angular.module('app').run(function () {
    (function(designWidth, maxWidth) {
        var doc = document,
            win = window,
            docEl = doc.documentElement,
            remStyle = document.createElement("style"),
            tid;

        function refreshRem() {
            var width = docEl.getBoundingClientRect().width;
            maxWidth = maxWidth || 540;
            width>maxWidth && (width=maxWidth);
            var rem = width * 100 / designWidth;
            remStyle.innerHTML = 'html{font-size:' + rem + 'px;}';

        }

        if (docEl.firstElementChild) {
            docEl.firstElementChild.appendChild(remStyle);
        } else {
            var wrap = doc.createElement("div");
            wrap.appendChild(remStyle);
            doc.write(wrap.innerHTML);
            wrap = null;
        }
        //要等 wiewport 设置好后才能执行 refreshRem，不然 refreshRem 会执行2次；
        refreshRem();

        win.addEventListener("resize", function() {
            clearTimeout(tid); //防止执行两次
            tid = setTimeout(refreshRem, 300);
        }, false);

        win.addEventListener("pageshow", function(e) {
            if (e.persisted) { // 浏览器后退的时候重新计算
                clearTimeout(tid);
                tid = setTimeout(refreshRem, 300);
            }
        }, false);

        if (doc.readyState === "complete") {
            doc.body.style.fontSize = "16px";
        } else {
            doc.addEventListener("DOMContentLoaded", function(e) {
                doc.body.style.fontSize = "16px";
            }, false);
        }
    })(750, 640);

});